In the Chemnitz Basin (Saxony, central Germany), up to 1,500 m thick early Permian sediments with intercalated, predominantly acidic pyroclastics were deposited. Numerous fossil records allow a biostratigraphic correlation of the strata with other early Permian successions of the middle Variscides. Significant floral and faunal elements were found in the Planitz Formation of the Chemnitz Basin, which is bounded at the base by the Grüna Tuff and at the top by the Planitz Ign-imbrite. Radioisotopic data are only available for the Planitz Ignimbrite, but they contradict biostratigraphic data. Based on LA-ICP-MS measurements, new U-Pb zircon ages are determined for the Planitz Ignimbrite and, for the first time, also U-Pb zircon ages for the Grüna Tuff. The challenge of deriving an extrusion age for both the Planitz Ignimbrite and Grüna Tuff from these data is discussed.